+* fs (file backend)
+ A fuller featured file based backend. Doesn't need any external
+ libraries and supports the full range of operations (such as text and
+ subkey searching). Needs a good filesystem to get good performance
+ though as it creates many, many files and links.
+
+* hkp
+ A proxying backend. No keys are stored locally; all fetch and store
+ requests are forwarded to the provided keyserver.
+